1. Field of the Invention
The present invention relates to a sound field generation system that generates a sound field space where the listener can receive spatial sound impression similar to that obtained in the case where the listener listens to music in, for example, a concert hall.
2. Description of the Related Art
As a sound field generation system of this kind, known is a sound field generation apparatus which is disclosed in JP-A-8-130799.
As shown in FIG. 10A, the sound field generation apparatus of the related art comprises reverberation generating circuits 1 and 2 which are called SFC processing circuits, filter circuits 3 and 4, adders 5 and 6, and amplifiers 7 and 8, and is configured so as to operate two speakers 9 and 10 to generate sounds, thereby generating a reproduction sound field where spatial sound impression can be obtained.
Each of the reverberation generating circuits 1 and 2 comprises a delaying circuit 13 having multistage delay elements D1 to Dn shown in FIG. 10B. Plural delayed outputs with respect to an input signal Sin are added to one another in a predetermined combination relationship, to generate signals for two channels which are provided with reverberation characteristics.
The reverberation generating circuits 1 and 2 further comprise an attenuator and an all-pass filter. The amplitudes and phase characteristics of the signals for two channels are adjusted, so that a right-channel signal SR1 and a left-channel signal SL1 are generated and supplied to the adders 5 and 6.
Each of the filter circuits 3 and 4 is configured by a variable filter which variably adjusts the gain of the right- or left-channel signals SR1 or SL1 in the audio frequency band as schematically shown in FIG. 10C. The output of the filter circuit 3 is supplied to the adders 5 and 6, that of the filter circuit 4 is supplied to the adder 6, and an inverted output of the filter circuit 4 is supplied to the adder 5.
According to this configuration, the adders 5 and 6 output right- and left-channel signals SR2 and SL2 which are similar to those recorded in, for example, a specific concert hall, and the signals SR2 and SL2 are supplied to the speakers 9 and 10 via the amplifiers 7 and 8, respectively, thereby generating a reproduction sound field where the listener can receive spatial sound impression similar to that obtained in the case where the listener listens to music in the specific concert hall.
Microphones 11 and 12 pick up reproduced sounds which reach from the speakers 9 and 10 to the ears of the listener. On the basis of obtained pick-up signals PR and PL, an interaural correlation coefficient xcfx81RL is acquired. The frequency characteristics of the filter circuits 3 and 4 are adjusted so that the difference between an interaural correlation coefficient xcfx81RLxe2x80x2 which is previously acquired from the actual transfer function (frequency characteristics) of the specific concert hall, and the interaural correlation coefficient xcfx81RL becomes zero.
The transfer function (frequency characteristics) of a listening room or the like of the listener is different from that of the specific concert hall. Therefore, the frequency characteristics of the filter circuits 3 and 4 are adjusted so as to approximate the interaural correlation coefficient xcfx81RL of the reproduction sound field which is actually generated in the listening room or the like to the interaural correlation coefficient xcfx81RLxe2x80x2 of the specific concert hall, so that, even in a listening room or the like of the listener, a reproduction sound field where spatial sound impression similar to that obtained in the specific concert hall is obtained is generated.
In the sound field generation apparatus according to the related art, the frequency characteristics of the filter circuits 3 and 4 are adjusted in the following manner.
First, it is assumed that the interaural correlation coefficient xcfx81RLxe2x80x2 which is previously obtained from the actual transfer function (frequency characteristics) of the specific concert hall has the characteristics shown in FIG. 11A. The transfer functions of the reverberation generating circuits 1 and 2 are previously set so as to coincide with the interaural correlation coefficient xcfx81RLxe2x80x2.
As shown in FIG. 11B, the passbands of the filter circuits 3 and 4 are set to a narrow band W1, and a stationary random signal of the narrow band is supplied as the input signal Sin for adjustment, thereby causing the speakers 9 and 10 to generate reproduced sounds based on the stationary random signal of the narrow band. The microphones 11 and 12 pick up the reproduced sounds, and the interaural correlation coefficient xcfx81RL is acquired on the basis of the obtained pick-up signals PR and PL. Thereafter, the difference between the interaural correlation coefficients xcfx81RLxe2x80x2 and xcfx81RL in the narrow band W1 is acquired.
Similarly, the passbands of the filter circuits 3 and 4 are sequentially switched to narrow bands W2, W3, . . . , Wk in this sequence, the speakers 9 and 10 are caused at each of the switching operations to generate reproduced sounds based on the stationary random signal of the narrow band, and the differences between the interaural correlation coefficients xcfx81RLxe2x80x2 and xcfx81RL in the narrow bands W2, W3, . . . , Wk are acquired.
The gains of the filter circuits 3 and 4 for each of the narrow bands W1, W2, W3, . . . , Wk are adjusted so that the difference between the interaural correlation coefficient xcfx81RL which is actually acquired for each of the narrow bands W1, W2, W3, . . . , Wk, and the interaural correlation coefficient xcfx81RLxe2x80x2 of the concert hall or the like becomes zero, thereby adjusting the frequency characteristics of the filter circuits 3 and 4 in the whole audio frequency band. Namely, the frequency characteristics of the filter circuits 3 and 4 are adjusted in consideration of the transfer function (frequency characteristics) of a listening room or the like of the listener.
When the frequency characteristics of the filter circuits 3 and 4 are adjusted in this way, the adders 5 and 6 outputs the signals SR2 and SL2 which are obtained by finely adjusting the signals SR1 and SL1 that have been provided with reverberation characteristics of the listening room or the like, on the basis of the output signals of the filter circuits 3 and 4. The speakers 9 and 10 are caused to generate sounds on the basis of the signals SR2 and SL2, with the result that, even in the listening room or the like of the listener, a reproduction sound field where spatial sound impression similar to that obtained in the specific concert hall is obtained can be generated.
When a stationary random signal of the narrow band is supplied as the input signal Sin for adjustment and the passbands of the filter circuits 3 and 4 are set in the sequence of the narrow bands W1, W2, W3, . . . , Wk as described above, the interaural correlation coefficient xcfx81RL is acquired with including signal components in the overlapping portions of the narrow bands W1, W2, W3, . . . , Wk as indicated by the hatched areas in FIG. 11C.
When the narrow bands W1 and W2 are considered, for example, since the bands overlap with each other, the interaural correlation coefficient xcfx81RL, which is acquired on the basis of the stationary random signal of the narrow band W1, contains influences of the stationary random signal in the narrow band W2, and the interaural correlation coefficient xcfx81RL, which is acquired on the basis of the stationary random signal of the narrow band W, contains influences of the stationary random signal in the narrow band W1. Also the interaural correlation coefficients xcfx81RL which are acquired for the other narrow bands W2, W3, . . . , Wk contain similar influences, respectively.
Even when the frequency characteristics of the filter circuits 3 and 4 are adjusted so as to perform approximation to the interaural correlation coefficient xcfx81RLxe2x80x2 of the specific concert hall on the basis of the interaural correlation coefficient xcfx81RL which is actually acquired, therefore, an approximation error may occur. As a result, there arises a problem in that a case may occur where, even when the input signal Sin of the actual audio frequency band is supplied to sound the speakers 9 and 10, the reproduction sound field cannot be approximated to the specific concert hall with sufficiently high accuracy.
The invention has been conducted in view of the problem of the related art. It is an object of the invention to provide a sound field generation system of a novel configuration which can generate a target sound field space where spatial sound impression simulating that obtained in, for example, a specific concert hall is obtained, with accuracy that is higher than that of the related art.
In order to attain the object, the invention provides a sound field generation system performing interaural correction on at least one input signal to generate a target reproduction sound field, comprising:
at least two sound releasing units;
two input lines through which the one input signal is supplied to the sound releasing units;
a plurality of first band splitting units which are disposed in at least one of the two input lines, and which have different bands from each other;
a plurality of delaying units which are disposed in the first band splitting units, respectively;
a sound picking unit adapted to pick up sounds released from the sound releasing units, at listening positions corresponding to both ears;
a plurality of second band splitting units adapted to band-split outputs of the sound picking units with the same bandwidths as those of the first band splitting units;
a calculating unit adapted to calculate interaural correlation on a basis of band-split outputs from the second band splitting units; and
a controlling unit adapted to control delaying amounts of the delaying units on a basis of a calculation result of the calculating unit.
According to this configuration, the input signal is supplied to the sound releasing units through the first band splitting units and the delaying units, and reproduced sounds are then generated. The sound picking unit at the listening positions pick up the reproduced sounds, and the outputs of the sound picking units are band-split by the second band splitting units. The calculating unit calculates interaural correlation on the basis of each of band-split outputs which have undergone the band split. Based on a result of the calculation, the controlling unit controls the delaying amounts of each of delaying units which is disposed in each of first band splitting units. When the delaying amounts of the delaying units are controlled in this way, a target reproduction sound field can be generated by the reproduced sounds released from the sound releasing units.
When the first and second band splitting units have the same band width, the result of the calculation of the interaural correlation contains no influence between the split bands. When the delaying amounts of the delaying units which are respectively disposed in the first band splitting units are controlled on the basis of the calculation result, the target reproduction sound field can be realized with high accuracy.
The system is configured so that attenuation factor adjusting units is disposed in each of the delaying units and the attenuation factors of the attenuation factor adjusting units are controlled on the basis of the calculation result of the calculating unit. According to this configuration, not only the delaying amounts of the input signal for the respective bands which are set by the first band splitting units, but also the amplitudes are controlled. Therefore, the target reproduction sound field can be generated with higher accuracy.
The invention provides also a sound field generation system performing interaural correction on at least one input signal to generate a target reproduction sound field, comprising:
at least two sound releasing units;
two input lines through which the one input signal is supplied to the sound releasing units;
a plurality of first band splitting units which are disposed in at least one of the two input lines, and which have different bands from each other;
a plurality of delaying units which are disposed in the first band splitting units, respectively;
a storage unit adapted to store transfer functions of spaces between the sound releasing units and listening positions at which reproduced sounds output from the sound releasing units are received, and which correspond to both ears, respectively;
a calculating unit adapted to perform a modulation process on the signal supplied from the input lines toward the sound releasing units on a basis of data indicative of the transfer functions, thereby generating modulated data corresponding to the reproduced sounds at the listening positions, the calculating unit adapted to calculate interaural correlation at the listening positions on a basis of the modulated data; and
a controlling unit adapted to control delaying amounts of the delaying units on a basis of a calculation result of the calculating unit.
According to this configuration, data (modulated data) of the sounds reaching to the listening positions are obtained by performing a modulation process on signals supplied from the input lines toward the sound releasing units on the basis of data indicative of the transfer functions (frequency characteristics) of the spaces between the sound releasing units and the sound picking unit. That is, data of sounds, which are released from the sound releasing units and reach to the listening positions, are acquired as pseudo sound data (modulated data) by so-called simulation. Furthermore, interaural correlation is calculated on the basis of the pseudo sound data (modulated data), and the delaying amounts of the delaying units are optimized based on a result of the calculation. Even when sounds released from the sound releasing units are not actually picked up at the listening positions, therefore, the delaying amounts of the delaying units can be optimized.
Furthermore, the system is characterized in that a plurality of attenuation factor adjusting units are disposed in each of the delaying units and the attenuation factors of the attenuation factor adjusting units are controlled on the basis of the calculation result of the calculating unit. According to this configuration, not only the delaying amounts of the input signal for the respective bands which are set by the first band splitting units, but also the amplitudes are controlled by simulation. Therefore, the target reproduction sound field can be generated with higher accuracy.